1. Field of the Invention
This invention relates to bearing systems for use in dirty environments and, more particularly, to apparatus and methods for bearing systems suitable for use on a pipeline inspection tool.
2. Background of the Invention
Oil, petroleum products, natural gas, hazardous liquids, water, and the like are often transported using pipelines. The majority of these pipelines are constructed from steel pipe. Once installed, a pipeline will inevitably corrode or otherwise degrade. Proper pipeline management requires identification, monitoring, and repair of defects and vulnerabilities of the pipeline. For example, information collected about the condition of a pipeline may be used to determine safe operating pressures, facilitate repair, schedule replacement, and the like.
Typical defects of a pipeline may include corrosion, gouges, dents, cracks, and the like. Corrosion may cause pitting, general wall loss, or cracking, thereby lowering the maximum operating pressure of the pipeline. Vulnerabilities may also include combined stress and chemical or biological action such as stress corrosion cracking. Without detection and preemptive action, all such defects and vulnerabilities may lead to pipeline failure.
Information on the condition of a pipeline is often collected using an in-line inspection (ILI) tool. While collecting such information, an in-line inspection tool is exposed to the adverse environment within a pipeline. That is, pipelines carrying material such as crude oil, natural gas, petroleum products, and raw water typically operate with both high pressure and suspended debris. This environment is often worsened by the presence on an in-line inspection tool, which tends to loosen and stir settled debris as it passes through the pipeline.
The adverse pipeline environment can damage an in-line inspection tool. For example, bearings used on an in-line inspection tool are susceptible to frequency failure. Attempts have been made to seal bearings for use in dirty environments. However, in a high pressure environment like a pipeline, seals tend to be limited in their effectiveness.
In view of the foregoing, what is needed is a debris resistant bearing suitable for use in dirty environments such as the environment within a pipeline.